Unprinting and Reusing Pollen-Based Paper
New ideas for sustainable materials are sprouting up like flowers in spring. One example of an alternative to conventional paper is pollen-based paper made from sunflowers, which can be reused several times thanks to a unique unprinting method.
A team from Nanyang Technological University in Singapore has made paper from a very particular material: pollen. To be precise, from the pollen of sunflowers. This organic material comes with many advantages, most notably in terms of recycling and sustainability.
"[B]y extending the lifespan of the paper […] we get the maximum value out of each piece of paper we produce,"
said NTU President and Professor Subra Suresh, who co-led the researchSafe, Strong and Sustainable
The first thing that comes to mind when thinking about pollen is likely to be allergies. But no need to worry – all substances that trigger allergies are removed during the production of the pollen-based paper. In terms of quality, there is no reason to be concerned either: pollen-based paper can keep up with conventional ones. Colors may appear differently, but the image resolution and clarity remain comparable. The tensile strength is also the same as that of standard paper.
This paper is actually one step ahead in sustainability issues. The production of it is as environmentally friendly as it is simple, and even the recycling is quite remarkable. Thanks to a unique unprinting method, it can be reused up to eight times.
Easy and Eco-Friendly Production
As already mentioned, the production of pollen-based paper is simple and environmentally friendly. Similar to the production of soap, potassium hydroxide is used to remove the cellular components from the sunflower pollen grains in the first step before converting them into a soft microgel in the next step. At this point, the allergenic substances are also removed from the material. With the help of de-ionized water, all residues are cleaned from the resulting pollen microgel. Finally, the gel is tipped into a mold and air dried.
Since humidity could bend and curl the pollen-based paper, it must be stabilized beforehand by immersion in acetic acid. Once this is done, there is nothing to prevent this paper from being used over and over again.
About the Unprinting Method
The so-called unprinting method removes the print on paper so the paper can be printed on again. Of course, this does not work with every type of paper – but it certainly works with pollen paper.
During unprinting, paper is immersed in an alkaline lab reagent for two minutes, which mechanically disintegrates and breaks the toner layer. Then, it is put into ethanol for five minutes, which causes it to shrink. After an air drying process, it can be reused up to eight times without any loss in structural integrity or the quality of the printed images.
